RDMA/rtrs-srv: Replace device_register with device_initialize and device_add

There are error cases when we will call free_srv before device kobject is
initialized; in such cases calling put_device generates the following
warning:

 kobject: '(null)' (000000009f5445ed): is not initialized, yet
 kobject_put() is being called.

So call device_initialize() only once when the server is allocated. If we
end up calling put_srv() and subsequently free_srv(), our call to
put_device() would result in deletion of the obj. Call device_add() later
when we actually have a connection. Correspondingly, call device_del()
instead of device_unregister() when srv->dev_ref falls to 0.

Fixes: 9cb83748 ("RDMA/rtrs: server: main functionality")
Link: https://lore.kernel.org/r/20200811092722.2450-1-haris.iqbal@cloud.ionos.comSuggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Md Haris Iqbal <haris.iqbal@cloud.ionos.com>
Reviewed-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/rtrs/rtrs-srv-sysfs.c

@@ -182,16 +182,16 @@ static int rtrs_srv_create_once_sysfs_root_folders(struct rtrs_srv_sess *sess)
 	 * sysfs files are created
 	 */
 	dev_set_uevent_suppress(&srv->dev, true);
-	err = device_register(&srv->dev);
+	err = device_add(&srv->dev);
 	if (err) {
-		pr_err("device_register(): %d\n", err);
+		pr_err("device_add(): %d\n", err);
 		goto put;
 	}
 	srv->kobj_paths = kobject_create_and_add("paths", &srv->dev.kobj);
 	if (!srv->kobj_paths) {
 		err = -ENOMEM;
 		pr_err("kobject_create_and_add(): %d\n", err);
-		device_unregister(&srv->dev);
+		device_del(&srv->dev);
 		goto unlock;
 	}
 	dev_set_uevent_suppress(&srv->dev, false);
@@ -216,7 +216,7 @@ rtrs_srv_destroy_once_sysfs_root_folders(struct rtrs_srv_sess *sess)
 		kobject_del(srv->kobj_paths);
 		kobject_put(srv->kobj_paths);
 		mutex_unlock(&srv->paths_mutex);
-		device_unregister(&srv->dev);
+		device_del(&srv->dev);
 	} else {
 		mutex_unlock(&srv->paths_mutex);
 	}

drivers/infiniband/ulp/rtrs/rtrs-srv.c

@@ -1336,6 +1336,7 @@ static struct rtrs_srv *__alloc_srv(struct rtrs_srv_ctx *ctx,
 	uuid_copy(&srv->paths_uuid, paths_uuid);
 	srv->queue_depth = sess_queue_depth;
 	srv->ctx = ctx;
+	device_initialize(&srv->dev);
 
 	srv->chunks = kcalloc(srv->queue_depth, sizeof(*srv->chunks),
 			      GFP_KERNEL);